Microsoft Corporation unveiled a new virtual assistant for Windows Phone devices Wednesday as it seeks to gain traction in a highly competitive and lucrative market for smartphones.

The assistant, Cortana, is named after an artificial-intelligence character in the company's ''Halo'' video games. Cortana tries to be chatty like Apple's Siri, while anticipating information you might want, like Google Now.

Cortana is among the new features coming to a Windows Phone update called 8.1. The updated operating system will come with new phones in about a month, including three that Nokia announced Wednesday. It will also be available as a free download for existing phones a few months later.

Microsoft Corporation is also updating its Windows 8.1 system for tablets, laptops and desktops. Although Microsoft Corporation has been pushing touch-screen controls, the new update is designed to make it easier for those with traditional keyboard and mouse controls. The update, simply called Windows 8.1 Update, is available starting next Tuesday.

Joe Belfiore, vice president of the operating system group at Microsoft Corporation, holds a pair of mobile phones featuring the new Windows 8.1 operating system during the company's "build" conference in San Francisco. (Reuters)

The announcements come as Microsoft Corp. opened its annual Build conference in San Francisco. The conference is aimed at developers who write software for Microsoft systems, though it's also a chance for the company to showcase its products more broadly and to build interest among the digitally connected.

Most of the new features relate to Windows Phone, a system that hadn't received as much attention as the main Windows system in recent years. But it's an area where Microsoft sees growth opportunities and underscores its commitment to mobile devices and services under new chief executive Satya Nadella.

Windows Phone had less than 5 percent of the smartphone market last year, according to Gartner. But unlike traditional PCs, people tend to upgrade phones more frequently. Many people in emerging markets are also getting smartphones for the first time.

To enable manufacturers to make devices more cheaply, Microsoft is giving away its operating system, something Google already does with Android. Manufacturers will be able to get the system for free for use on phones and tablets with screens of less than 9 inches diagonally. Android carries no size restriction.

With the Cortana assistant, Microsoft catches up to Siri and Google Now in